1. Field of the Invention
The present invention relates to a surface isolation device, and more particularly, to a surface isolation device for isolating a wafer from an etching solution during the fabrication of a print head.
2. Description of the Prior Art
Today""s computer users are becoming increasingly knowledgeable about technology. As a result they are demanding better and cheaper computer peripherals for making hard copies of their documents. Due to their high print quality and low cost, ink jet printers are extensively used to print documents. A typical inkjet printer comprises a print head, and documents are printed by ejecting ink droplets from several nozzles in the print head onto paper. The print head comprises at least one manifold and several chambers. The manifold is used to supply ink to the chambers. Each chamber comprises a nozzle, the nozzle comprising an orifice and a pressurizing device. The pressurizing device is normally a heater that is used to heat the ink in the chamber to produce bubbles, which push the ink out of the chamber in the form of ink droplets.
The manifolds are usually formed internally in the print head. In the early days of print head manufacturing, sandblasting processes were performed to form the manifolds in the print head. However, sandblasting is a low-precision process and causes deviations in the positions of the manifold and rough edges, negatively affecting the quality and yield of the print heads. In order to prevent the above-mentioned problems, the manifold fabrication method using sandblasting processes has been gradually replaced by a method where manifolds are produced by performing an etching process on a single crystal wafer. However, this etching process includes forming a hole as the manifold, so the required time for the etching process would be relatively long. Because etching solutions are usually strong acids or strong bases, the wafer can be easily damaged and cracked during lengthy etching processes. In addition, if another circuit, such as a heater is already formed on the wafer, the heater will be affected by the etching solutions and may not operate normally.
Methods have been devised to decrease damage caused to the wafer and the circuit by the etching solution. In prior art methods, such as U.S. Pat. No. 5,841,452 xe2x80x9cMethod of fabricating bubble jet print devices using semiconductor fabrication techniques,xe2x80x9d when performing a lengthy etching process, a hard passivation film is deposited on the top and bottom of the wafer. After formation of the etching patterns, the wafer is put into the etching solution to be etched. FIG. 1 to FIG. 3 illustrate how circuits on a wafer 10 are isolated from an etching solution by a passivation film according to the prior art. Before an etching solution is used to etch the wafer 10 to form an orifice 18 and a chamber 20, other circuits, such as a heater 12 and a transistor 14, are formed on the wafer 10. In order to isolate these circuits from the etching solution, a glass layer 16 is deposited on the wafer 10 after forming the heater 12 and the transistor 14. The glass layer 16 acts as a passivation film for isolating the heater 12 and the transistor 14 from the etching solution. However, the process of depositing the glass layer 16 is complicated and when the etching solution etches the wafer 10, tiny holes can sometimes form at the edge of the wafer 10. These tiny holes decrease the density of the wafer and even affect the yield of forming manifolds. In addition, when depositing the glass layer 16 on the wafer 10, coating holes sometimes form on the glass layer 16. When coating holes form on the glass layer 16, the etching solution can flow through the coating holes onto circuits on the wafer. Therefore, a passivation layer formed on the wafer 10 is not ideal for isolating circuits on the wafer 10 from etching solution.
It is therefore an object of the claimed invention to provide a surface isolation device for isolating a surface of a wafer from an etching solution during a manifold etching process. The surface isolation device also isolates an edge of the wafer so that an etching process can be performed after the formation of a front circuit of the wafer without decreasing the wafer density.
In the claimed invention, the surface isolation device comprises a base for positioning a wafer, a fixture for fixing the wafer to the base, and an isolation ring positioned on the base for isolating a predetermined area of the wafer from etching solution. When the fixture fixes the wafer to the base, the wafer adheres to the isolation ring so as to isolate the predetermined area from the etching solution.
These and other objectives of the claimed invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiments that are illustrated in the multiple figures and drawings.